Presently, there are great demands for, the improvement of the compression efficiency of a reciprocating-type hermetic compressor used for a cooling system, such as a refrigerator or a freezer.
A conventional hermetic compressor of this type is disclosed in U.S. Pat. No. 4,723,896, and constructed as follows. The volume of a discharge hole arranged on a valve plate is made small so as to improve compression efficiency. Also, a reed valve is positioned on the discharge hole of the valve plate, and a supporting spring, a valve stopper and a retaining spring are arranged on the reed valve, thus temporarily retaining these members. When a cylinder head is secured to a cylinder block, the retaining spring is pressed so as to secure the cylinder head and the cylinder block.
However, such a conventional hermetic compressor has a problem in that testing of correct positioning of the reed valve for closing the discharge hole and the spring reed for urging the reed valve in the closing direction so as to yield proper operation cannot be performed using only these two members.
Also, in a machine having a greater cylinder volume, having only a single discharge hole might increase the over-compression loss, thus causing a reduction in the compression efficiency. The over-compression loss is caused by the following phenomenon. When the pressure within a cylinder reaches a high level, and such a high pressure slightly exceeds the opening pressure of a discharge reed valve, the discharge reed valve is opened. The small difference between the high pressure and the opening pressure of the discharge reed valve causes the over-compression loss.